It is one easy to install and manage vitualization technique. Its pretty fast also, compared to some other vitualization techniques. And that is because its has a very small amout of resource overhead. It lacks the server console which decreases its booting time.
Room for Improvement:
We can say its free but it's not. Free versions has limited capabilities and misses some very strong features. So in my opinion its not free. Other then that, it misses the console, which may be good from booting point of view, but from troubleshooting point of view, its bad. As it takes a lot more administrations skills to tackle problem without the proper control panes in the form of the console panel.